Since our introduction of DoNotTrack.Us last week we've received a deluge of questions. This post answers some of the most common inquiries. If we haven't covered an issue you'd like a response on, shoot us an email and stay tuned - more Q & A posts are in the pipeline.

Q: Do Not Track does not block third-party tracking. Wouldn't that be a better solution?

Some privacy-conscious users block third-party tracking, most commonly through browser add-ons. This type of self-help is completely compatible with and complementary to Do Not Track; many Do Not Track users may elect to use blocking software. But blocking alone is not a complete solution to web tracking. Here are our chief concerns:

Universal blocking is infeasible. Web security research (1, 2, 3) has uncovered dozens of means of tracking users; technical barriers to all these approaches are not practical. And a recent informal study of popular Firefox blocking add-ons suggests that blocking is, in practice, far from a universal opt out. Users should not be left guessing as to whether they've actually opted out of tracking.

Blocking software requires perpetual development and user vigilance. There is frequent turnover of tracking services and tracking technologies. If a developer takes a break, its blocking tool will diminish in effectiveness. Users must, consequently, periodically ensure their blocking software is still maintained and up-to-date.

Blocking inhibits third-party tools. A number of popular website tools and plug-ins are hosted by a third party that also tracks users. Blocking would disable these tools, while Do Not Track accommodates them.

The web privacy debate is stuck. Privacy proponents decry the diffusion of behavioral advertising and tracking services (1, 2, 3); industry coalitions respond by expounding the merits of personalized content and advertising revenue (1, 2). But for the average user, the arguments are academic: there is no viable technology for opting out of web tracking. A registry of tracking services, like privacy advocates proposed years ago, is cumbersome and unmanageable. Fiddling with cookies, as many advertising networks and anti-regulation advocates recommend, is an incomplete and temporary fix; both Google and NAI (an advertising industry association) have already moved away from opt-out cookies.

Do Not Track ends this standoff. It provides a web tracking opt-out that is user-friendly, effective, and completely interoperable with the existing web. The technology is simple: whenever your web browser makes a request, it includes an opt-out preference. It's then up to advertisers and tracking services to honor that preference – voluntarily, by industry self-regulation, or by law.

Arvind Narayanan and I have been researching Do Not Track for several months, and are pleased to now introduce DoNotTrack.Us, a compilation of what we've learned. The resource explains Do Not Track, provides prototype implementations, and answers some common questions. We'll be updating it in the coming months with new findings and responses to feedback.

Excited as we are about the Do Not Track technology, it is but a first step. Important substantive policy questions remain open: What tracking should be impermissible? When a user visits a site, what constitutes a third party? We look forward to collaborating with advertising networks, NGO's, regulators, lawmakers, and other stakeholders in answering these crucial questions.

Late last year the Obama administration reopened talks with Russia over the militarization of cyberspace and assented to cybersecurity discussion in the United Nations First Committee (Disarmament and National Security). My intention in this three-part series is to probe Russian and American foreign policy on cyberwarfare and advance the thesis that the Russians are negotiating for specific strategic or diplomatic gains, while the Americans are primarily procedurally invested owing to the “reset” in Russian relations and changing perceptions of cyberwarfare.